THE BLIND-FISHES. 



123 



overlying structures, and over the liver, which can be seen 

 through the translucent sides and ventral wall. About the 

 head and bases of the fins the color is yellowish, resembling 

 diluted blood. The surface of the body is slightly iridescent, 

 and the surface of the head has a velvety, peach-bloom appear- 

 ance. 



The general pink color of Amblyopsis is due to the blood. 

 It is not due to any abnormal development of blood vessels in 

 the dermis. In the fins, where the blood vessels are near the 

 surface, the general effect is a yellowish color. The surface 

 vessels of the dermis also appear yellowish. It is only on 

 account of the translucent condition of all the tissues, permit- 

 ting the deeper vessels to show through a certain thickness, 

 that the pink effect is produced. Amblyopsis has always been 

 spoken of as white. The term " white aquatic ghosts " of Cope 

 is very apt, for they do appear white in the caves, and their 

 gliding motion has an uncanny effect. All alcoholic specimens 

 are white. 



The chromatophores in Amblyopsis are differentiated and 

 contain color before the yolk is absorbed. The black chro- 

 matophores are minute granules, few (fifteen or thereabout) to 

 the segment. In an older larva the pigment was much more 

 abundant. The eyes are pigmented early, — shortly before hatch- 

 ing, — and, owing to their pigment, they soon become conspicu- 

 ous and remain so till the fish has reached 50 mm. in length, 

 when the overlying tissues have become thick. The pigment 

 of the body is lost, or, what amounts to the same thing, does 

 not increase much with age. There is an abundance of pig- 

 ment cells in the adult, but they are very poor in pigment, and, 

 being in the dermis and covered by the thick layer of epidermis 

 rich in glands, are not apparent. Pigment cells are also abun- 

 dant in deeper tissues in the adult, so that, while no pigment is 

 visible on the surface, an abundance of chromatophores are 

 present in deeper tissues. 



The pigment cells cannot be made to show themselves even 

 by a prolonged stay in the light. The old, if kept in the light, 

 will not become darker, and a young one reared in the light 

 until ten months old not only showed no increase in the pig- 



